Radiation examination devices such as an X-ray CT (Computed Tomography: CT) device have been used for various applications including medical use, industrial use, and so on. As the radiation examination device, for example, a multi-slice X-ray CT device having a scintillator array mounted thereon can be cited. The multi-slice X-ray CT device enables overlaying of sliced images and three-dimensional display of a CT image.
The scintillator array has a plurality of detection elements (photodiodes or the like) arranged in a matrix in a plane. Further, a radiation detector to be mounted on the radiation examination device includes a plurality of scintillators provided every single detection element. In the radiation examination device, X-rays entering the scintillators are converted into visible light and the visible light is converted into electrical signals by the detection elements, thereby obtaining an image. In recent years, in order to obtain high resolution, the detection elements are miniaturized to thereby narrow a pitch between the plural detection elements. The size of the scintillator is preferred to be small with miniaturization of the detection element.
As a material of the scintillator, for example, a gadolinium oxysulfide sintered body can be cited. For example, a ceramic scintillator made of the gadolinium oxysulfide sintered body has a fixed color body with chromaticity coordinates (x, y). The chromaticity coordinates are measured by using a color meter, for example. The minimum diameter that can be measured by a general color meter falls within a range of about 2 mm or more to 8 mm or less. A measurement area when the diameter is 2 mm or more and 8 mm or less is, for example, 3.14 mm2 or more and 50.24 mm2 or less. The chromaticity of a measured region is sometimes found to be in an appropriate range within the above-described measurement area range even when minute foreign matters are present.
When the ceramic scintillator is small in size, the effect on emission characteristics is likely to be large even when a slight composition deviation occurs. Therefore, when the composition deviation occurs, an optical output that converts X-rays into visible light sometimes decreases. Further, in a scintillator array including a plurality of ceramic scintillators arranged in a matrix in a plane, the optical output between the ceramic scintillators decreases, and thereby sensitivity as the scintillator array decreases.